Process of obtaining cold sepia tones



Aug. 19, 1952 B CQRRENT 2,607,686

y PROCESS 0F OBTAINING COLD SEIA TUNES Filed 06f. 18, 1949 WA VELENGTH/Nv M/LL/M/GRONS INVENTOR /PA f8. CURRENT Patented Aug. 19, 1952 PROCESSoF OBTAINING coLD f ToNEs j SEPIA .Y if

ra B. Current, Binghamton, N. Y., assigner to General Aniline & FilmCorporation, New York, v N. Y., Ya corporation of Delaware Applicationoctober 1s, 1949, 'serial No. 122,993 j solaims. (cias-488) Thisinvention relates to the toning of vdeveloped photographic prints andrparticularly to an improved process of obtaining cold sepiatones bysulfur or selenium toning of developed chloride and chloro-bromideemulsions. Y

It is known in the photographic art that metallic silver, which formsthe image of a photographic print or transparency, can be replaced witha compound of silver or other metal, such as sulfur, selenium, gold, tinand the like, by the toning process. The most generally used toningprocess consists of converting the metallicsilver to silver sulfide orsilver selenide to produce what are commonly known as sepia prints whichrange in color from a yellowish brown to ashade approaching purple.vsulfide and selenide toning methods may be either direct, in which `thesilver image is converted at once into an imager of silver sulfide orsilver selenide, or indirect, in which the silver image is firstconverted to a silver halide by bleaching, and then transformed into asulfide or selenide image in a bath containing soluble sulfide orselenide.

The color of a sulfide-toned printv depends upon the sizes andstructures of the grains of which the image is composed. A coarsegrainedstructure in the original silver print generally gives a tonev tendingtoward the purple.,while a fine grained print-generally produces a tonedprint of a yellowish brownshade. Forthis reason, both the nature `of theemulsion withwhichthe print is made, and the processing procedure usedin making a silver print have a bearing upon the color of theprint aftertoning has been carried out. For example, the development of the silverprint has a very important effect upon the color of the toned print. Ifa print is overexposed and underdeveloped, the grain structure is finerand the color of the toned print tends toward 'the yellow.

Considerable time and effort have been exthe prints should be developedprior to toning in a developer containing a specified amount of asoluble bromide-'for a fixed period of time. As a consequencey of thisunderstanding, several print developers containing specified amounts ofa soluble bromide have been devised for various positive emulsions. Forbromide and fast chlorobromide papers-ian Amidol (di-hydrochloride of2,4-diaminophenol) developer containing one gram of potassium bromide isgenerally used. A Metol-glycine-hydroquinone (p-methylaminophenolsulfate, p-hydroxyphenylglycine, and hydroquinone) developer containingfrom 3 to 4 grams of potassium bromide is generally used for chlorideand chloro-bromide papers, whereas for some chloride and slowchloro-bromide papers, a Metol hydroquinone developer containing from11A; to 2 grams of 'potassium bromide is generally used. For somebromide and chloro-bromide papers, a glycine-hydroquinone developercontaining as high asA 4 grams of potassium bromide has beenrecommended.

In developing positive chloride and chlorobromide emulsions withdevelopers normally used, i. e., those containing from 0.5-4 grams ofpotassium bromide per liter, warmer tones are obtained after sulfur orselenium toning. Despite the fact that these emulsions are available ina wide range of speeds, from the slow chloride type to the fastestpapers, substantially equal in speed to the fastest bromides, they allmay yield upon development with the recommended print dev velopers,followed by sulfur or selenium toning,

pended by investigators in devising satisfactory y methods of obtaininguniformly the` desired shades in sulfide and 'selenide toned. prints. Inthe field of portrait and pictorial photography, the positive emulsionsVused have lbeen formuflated to produce only a relatively warm tone upondevelopment. However, many photographers also desire to use the samepaper for sepia toning, but are disappointed by the extremely warm oryellowish sepia tones obtained, despite the fact that bromide emulsionstend to produce somewhat colder tones than either chloride orchlorobromide emulsions.

f It' has always been taught by the art that for greatest uniformity ofcolor and depth of tone,

. inafter. f

prints of warmer than desired character. It is an object of the presentinvention to providea 'method whereby cold sepia tones are;ob

tained by the toning of chloride and chlorobromide emulsions. Otherobjects and advantages will appear here- I havefound that contrary torecognized Vunderstandings yand established procedures, chloride I andchloro-bromide positive' emulsions, which normallyv yieldv warm tonesupon sulfur orv selenium toning, yield colder sepia tones by firstdeveloping the'exposed chloride and chlorobromide positive emulsion withany black and white print developer containingfrom 20 to 80 grams 1ofpotassium vbromide per liter of developer.,` With normal orv slightlyincreased developingtime, the prints are altered so that alvmost anydegree of colder (deeper brown) sepia and even bluish-black tones areobtained on sulfur or selenium toning. This unexpected result appears tobe due to the'high concentration of potassium bromide in the developer,which posgrowth (compared to an Ostwald ripening effect),

to give a tone eifect more nearly approaching that available from abromide paper. The amount of potassium bromide to be added to thedeveloper is governed by the kind of paper selected for making the printand the color tone desired. vFor a slow chloro-bromide and' a fast.

chloro-bromide or a chloride paper of moderate speed, as little as 20grams per literof potassium bromide is sufficient to produce anoticeable effect.V

`tones they represent become. :across With no ups or downs wouldrepresent a practically neutral or gray tone.

the tone is represented by the shape of the curve after development from4 to 8"minutes followed by toning. A'concentration of 50 grams per literof potassium bromide has been found to produce satisfactory cold tonesafter toning. Above 80 grams per literof addedfpotassium bromide, therestraining action may be so Ygrea-,tl that Vthae effectorthe'conversion of'the halide in the paper cannot bei realized and aWarmer than normal tonemay result. The exact limits of potassium bromideconcentration are dependent, therefore, uponpthe type of emulsion, i.Ve., Whethera chloride or a chloro-bromide; emulsion, the .desired tone,and the developing time, all of whichcan be very'readily ascertained bysimple trial experimentsK y f The .developers which may be vusedvinaccord-V ance'WithLthe present invention are thosewhich are normallyemployedffor` Adeveloping' out .positive silver halide emulsions. Asillustrative examples of vthereducing agentsY contained in suchdevelopers, the following are given: (a) p-liethylamincphelnol sulfateand hydroquinone Y (5) G lycin (p-hydroxyph'enylglycine) Y (c) lAdurol(2#brume1Adihydroxybenzene)' (d) Eikonogen V(hydrated sodiumaminoAnaph-v Athol Sulfonate) i n (e) Amidol (2;4-diaminophen'oldihydrochloride) ('f) Chlorhydro'quncne (2.-chloro-1fi-dihydroxybenzene)Print developers containing the -foregoingree ducing orV developing agents are availablein photographic literatureand need not be Arepro,-duced herein.

As pointed out above, .the developing time of the exposed printmay. varyfrom. 4 to 8 minutes. The usual. developing/,time With developers ofthis type, withoutfthe 4higli concentration Lof potassium bromide,normally usedfor-'developing exposed positive. emulsions. varies from;.L1/2; to 15 minutes. Withthesame developers containing from 20y to 80grams of potassium bromide-a minimum developing.. time of. about. 2,minutes may be necessary to yield satisfactory results. The developingtime must, in some cases fdepending. .uponf the typev of vprint paper,be .extended frornV to v1() minutes to' overcome the restrainingeffectief the potassium br'omidegfothervvise Vthe result may yield..warmer-.l tones .thanswould be obtained Withoutv the bromide addition.This makes vthe developingbtirnelan .important variable When using,prior toltoning, a developer cone taining a high concentration.v ofpotassium bromide, but Vif .it isextended enough, Vusually not more than8V to 1'01 minutes, reasonablyV repro` ducible colder toningresults willbe obtained warm tone printingpapers.V f

The present invention.. is. illustratedV by f thev accompanyingdrawing-in whichFigs. lfand 2` represent spectrophotometricrefiectanceE-curves 4 indicating the relative proportions of light ofdifferent wavelengths that are reected from the toned areas. In otherwords, the curves are graphic presentations of the relative color of thetones at an arbitrariiy chosen medium density (0.5) at Wavelength 400 atWhich the start of the -curves are selected. Although these curves donot show the `eiects of higher and lower densities which also influencethe color of the tone prints,

vthey serve, however, to show the relative toning effects. The higherthe right hand part of the curvesextend, the morereddish or warmer the Acurve straight The color of land even relatively minor variations in thecurve shape may be detected in the actual print by an experienced eye.

These curves were obtained by adjusting toned photographicprint Wedgesin thespectrophotometerf until the ton'edfdeposit-gave a reilectancereading of Y3 O at` a Wavelength,ofA 400 millimicrons..

Fig. 1 indicates'the natureofthetones obtained on a slow chlorof-bromidetpaperA withl a two r`minute developmentiin a high energy` devel,- opercontaining no potassium bromide and 20 and 80 grams per.liter-respectively, andthe subsequent. conversion of the Asilver imageintothe silver sulfide image.; Y

Fig s2..illustrates.;the` toning Veiect on a fast chloro-bromide paper.resulting fromI 8-rninute development in alovv energy developercontaining f no potassium bromide andff andai) gramsof bromide:projectionpaper'of moderatespeed were exposed;v Them-sti. paper:was,developed in a developer solutiorrofz. the following composition for.5 minutes: at 68? F.: f

Y prepared. as 'above;-except that the developing Frnithese lcurves, itwill be.observed .that/the addition vof 20 .and y8l) 'grams 'ofIpotassiumA .bromide. respectively, per literof-'developer producesexcellentcoldertones when followed by direct sepia toning.

ilExample-II A lTh'ree'shee'tsl'of al fast chloroebromideemulsionprojection paper were individuallyv-exposed through a-.nega'tiva The"first .exposed print was developed for 8 minutes at 682 C in adeveloper solutiofpf the following composition: Hotjwater}('l25 F. or 52C.) 1;.; cc l. A1750 The second and third"ei'qiolsedf` papers :weredeveloped in tw'or separate developing solutions prepared as above,except that thel developing solutions contained in addition 20 and 80grams of potassium bromide per liter, respectively.

After short-stopping, fixing, washing, and drying, the developed printswere toned :for 10 minutes at 72F. in a solution prepared as follows:

100 grams of sodium sulte are dissolved in a smallv amount of Water,then 10 grams of powdered selenium metal dissolved in this solution, andthe volume -brought up to 1 liter. The clear part of the solution may bedecanted or ltered from any sediment remaining and used as adirect'toning solution.

The toned prints were washed for minutes in flowing water and thendried.

Spectrophotometric curves of the resulting three images, at a density ofabout 0.5, were obtained as illustrated in Fig. 2. These kcurvesillustrate the somewhat less cold toning effects resulting from thedevelopment with bromide additions.

In lieu of the developing solutions of the foregoing examples thefollowing developer solution may be employed to yield the same coldertones when followed by direct sepia toning:

Hot water (125 F.) cc 750 p-Methylaminophenol sulfategrams.. 5 Sodiumsulflte do 40 Hydroquinone ..do 6 Potassium bromide do 50 Sodiumcarbonate (monohydrate) do 40 Water to make 1 liter.

Example III Three sheets of chloro-bromide projection paper wereprocessed up to and including the washing step described in Example I.

After washing the prints were bleached for 5 minutes in a solution ofthe following composition? Potassium ferricyanide grams-- 50 Potassiumbromide do 10 Water to make 1 liter.

The bleached prints were washed for 5 minutes and toned, i. e.,redeveloped. in a 1% solution of sodium sulfide in water.

'I'he toned prints were thoroughly `washed in water for 30 minutes anddried. Prints of excellent cold sepia tone were obtained.

-An optional hardening treatment with an aqueous chrome alum solutionmay be used on the toned prints prepared as above after some preliminarywashing so as to remove most of the 6 sodium sulde absorbed bytheemulsion layer;v Once a particular printgdeveloper containing from 20 to80 grams of potassiumfbromide-,per literhas beenfound whichgives thedesiredsepia tones,fa1l 'the'steps e., developer formula andconcentration "of 'potassium bromide o'uldfbe carefully standardized andmade yuniform from` one tim-e tothe next, and frequentv renewalo allprocessing solutions will insurev .uniformity of tones from .day to day..Onthe otherifhandgthe. factorseifecting the .sepia tones maybe-putte,an' advantage.. in securingalmostany.- degreefo'f. warmth and tone,.'particularly the1addition:of potassium bromide ranging .from v220 toy80, grams per liter to an energetic developer with increaseddeveiopirlgtiine, i. e.; frcm'at 1p mimiteswiiicn can' provide" -directsepia tones, 'considerably colder than Flemish tones available 'fromthe' same paper with normal print developer andvde-V veloping time1`-:ff nl -;'..'1,.": u f f IWhile I have herein vidiscl'osed the preferredembodimentslof my invention,vI doV not desirelt'o limit myself solely tothe specific examples since it will lbe readily apparent to thoseskilled in the art that the precise ratios of potassium bromide and thenature of the reducing agent in the print developer may be varied. Anyother reducing materials having equivalent properties may be employedwithout departing from the spirit and scope thereof. Accordingly,therefore, only such limitations should be imposed as are indicated inthe appended claims.

I claim:

1. A process of obtaining cold sepia tones by toning warm toned positiveprinting papers of the group consisting of chloride and chloro-bromidepapers which consists of exposing and developing said papers with aphotographic developer for positive silver halide emulsions comprisingan aromatic silver halide developing agent and from 20 to 80 grams ofpotassium bromide per liter, fixing and washing the developed print, andsubsequently toning it with a toner selected from the group consistingof sulfur and selenium toners.

2. A process of obtaining cold sepia tones by toning a warm toned silverchloride emulsion positive printing paper which consists of exposing anddeveloping said paper with a photographic developer for positive silverhalide emulsions comprising an aromatic silver halide de-` velopingagent and from 20 to 80 grams of potassium bromide per liter, fixing andwashing the developed print, and subsequently toning with a tonerselected from the group consisting of sulcomposition;

Hot water F.) cc 750 p-Methylaminophenol sulfate grams 5 Sodium sulte do40 Hydroquinone do 6 mamas Henney & Dudley. Handbook of Photpga-rzrfwMcGraw-Hill, 1937,*p. 369.

1. A PROCESS OF OBTAINING COLD SEPIA TONES BY TONING WARM TONED POSITIVEPRINTING PAPERS OF THE GROUP CONSISTING OF CHLORIDE AND CHLORO-BROMIDEPAPERS WHICH CONSISTS OF EXPOSING AND DEVELOPING SAID PAPERS WITH APHOTOGRAHIC DEVELOPER FOR POSITIVE SILVER HALIDE EMULSIONS COMPRISING ANAROMATIC SILVER HALIDE DEVELOPING AGENT AND FROM 20 TO 80 GRAMS OFPOTASSIUM BROMIDE PER LITER, FIXING AND WASHING THE DEVELOPED PRINT, ANDSUBSEQUENTLY TONING IT WITH A TONER SELECTED FROM THE GROUP CONSISTINGOF SULFUR AND SELENIUM TONERS.